In general, in order to acquire a distance from an image of an imaging apparatus to a subject in a 3D spatial depth map, i.e., in a 3D space, a stereo camera method, a laser scanning method, a Time of Flight (TOF) method, etc. are known.
Thereamong, the stereo camera method is carried out by executing a process of three-dimensionally recognizing a subject using two human eyes through hardware. One subject is captured by two cameras and depth (or distance) information in a space is extracted through an analysis process of a pair of acquired images.
In order to acquire distance information using a stereo camera, two cameras are required and distance or depth information may be acquired by calculating disparity between images respectively acquired from the two cameras on the same epipolar line.
However, since the two cameras respectively acquire images and depth or distance information may be acquired by measuring a matching degree between the two images, conventional depth map extraction requires precise alignment of the two cameras.
Further, although the two cameras are aligned at proper positions, geometric information, such as rotations, translations, focal distances, skew angles, and principle points of the two cameras, is required. After the epipolar lines of two images acquired from the two cameras based on the geometric information are coincided with each other, distance information may be acquired.
In order to acquire distance information through the above method using two cameras, a plurality of calibration processes is required and, in order to acquire accurate distance information, calibration needs to be performed again whenever mechanical deformation is generated due to environmental change.